The Goblins of the Kapûl-Doraz (Goblin-Town) were for the most part descendants of two different tribes. The first were Mountain Orcs who hailed from the north, descendants of Morgoth's Warrior-Orcs. The other - and more numerous - group were Deep-Orcs, small and degenerated Goblins hailing from the Underdeeps and descendants of the slave caste of Utumno. In the Second Age these Orcs were joined by Greater Orcs from Barad-dûr who had been sent by Sauron to take control and fortify the passes over the Misty Mountains such as the High-Pass and the Old Pass.These lackeys of Mordor quickly rose in the Mountain realm's hierarchy and made themselves the rulers of the indigenious goblin-clans and built the vast under-mountain realm known as Goblin-Town.
The clans of Goblin-Town were numberless, but collectively forged into one big tribal federation known as the Uruk-Tarkhnarb ("Orc. "Orcs of ranging Wounds"). The Tarkhnarb's traditional ruler was known as the Great goblin and usually an individual descending from the small bloodline of Ogslap , a scion of Morgoth's demon-Orcs, or Boldogs.
The Movie Trilogy shows the Orcs of Goblin-Gate as degenerated and primitively equipped Lesser Orcs, much similar and probably related to the Moria Goblins and the Snagas of Isengard and Mordor.Only a few of these orcs appear of greater statue, among them the grotesque Great Goblin.